Production of colored photographic images



Patented Mar. 12, 1946 PRODUCTION OF COLORED PHOTOGRAPHIC IMAGES DouglasWilliam Stammers,

Blackley, Mancheater, England, minor to Imperial ChemicBarll IndustriesLimited, a corporation of Great No Drawing. Application November 15,1943, Se-

rial No. 510,373. 25, 1942 In Great Britain November 4 Claims. (Cl.95-6) This invention relates to the production of colored photographicimages.

It is known that when a photographic silver halide emulsion is developedby treatment with an aromatic amino developing agent, for example, anasymmetric dialkyl p-phenylenediamine,

there is formed an image of metallic silver. It is also known that whenthere is present also in the developing solution or in the silver halideemulsion a suitable substance, known as, a color-former, which willreact with the oxidation product of the developer to produce a dyestufl'there is also formed simultaneously a colored photographic image. Thecolored image may be revealed by removal of the silver image bytreatment with a suitable bleaching agent, for example with that knownas Farmer's reducer.

According to the present invention I produce a photographic dyestuifimage in a photographic element either by developing a reducible silversalt contained in the element with an aromatic amino developing agent,as defined hereinafter, in the presence of a color former which is a2:4- diarylpyrrole of the formula where R and R. stand for aryl radicalsfor example of the benzene or naphthalene series, substituted or not,the same or difierent, and where R stands for hydrogen or for anon-reactive substituent, for example an aryl-, alkyl-, allgylamino-,benzylideneaminoor acylaminqradical, or by treatin a photographicelement containing such color former with an oxidation product of such adeveloping agent or with a p-nitrosodialkylaniline or with a diazoniumsalt.

The aromatic amino developing agents used are those which are capable ofdeveloping silver halide photographic emulsions and which are orp-phenylene diamines-or derivatives thereof containing at least oneunsubstituted aminogroup, or 0- or p-amino phenols or derivativesthereof containing an unsubstituted amino group.

Examples of such developing agents which may be used includep-aminodii'nethylaniline, p-aminodiethylaniline, p-aminodi-n-butylaniline, p methylaminoaniline, p ethylaminoaniline,chloro-p-phenylenediamine, 1 2 5-toluylenediamine,2-amino-5-diethylaminotoluene, N-paminophenylpiperidine,N-methyl-N-p-hydroxyethyl-p-phenylenediamine, N-n-butyl-N-p-hydroxyethyl-p-phenylenediamine, py-dihydroxy- February 10, 1943.

propyl-p-phenylenediamine and N:N-diethyl-ophenylenediamine.

The 2:4-diarylpyrro1es which may be used as color formers according tothe invention include. for example, 2:4-diphenylpyrrole,2-(p-methoxyphenyl) -4-phenylpyrrole, 2- (m-hydroxyphenyl)4-phenylpyrrole, 2-(o-chloropheny1) -4-phenylpyrrole, 2-(p-acetylaminophenyl) -4-phenylpyrrole, 2-e-naphthyl-4-phenylpyrrole,2-phenyl-4- B naphthylpyrrole, 2:3:4 triphenylpyrrole, 3-

benzoylamino-2-:4-diphenylpyrrole, 3-acetylamino-2 4-diphenylpyrrole and3- benzoylamino-2 4- di-p-tolylpyrrole. The sulphonic acid derivativesof the 2:4-diaryl pyrroles, for example of those listed above, and theirsalts, may also be used.

The 2:4-diarylpyrro1es which are used as color formers may be made, forexample, by the processes described in the specifications ofapplications Nos. 16,277/41 and 3,583/42, new British Patent No. 556,156and in the corresponding United States applications Serial No. 457,229,filed September 3, 1942, and Serial No. 475,434, filed Those2:4-diarylpyrroles which bear in the 3-position an amino or substitutedamino group may be made as is described, for example, in the case of3-benzoylamino-2z4- diphenylpyrrole, by Gabriel, in Berichte derdeutschen chemischen Gesellschaft, 41, 1138. The sulphonic acidderivatives of the 2:4-diarylpyrroles may be made, for example, as isdescribed in the specification of application No. 9,689/42 andcorresponding United States applition Serial No. 482,479, filed April 9,1943,

As said the photographic dyestufi image may be produced by developing areducible silver salt image with an aromatic amino developing agent inthe presence of the color formers of the invention.

' The color formers may be present in the developing solution or theymay be incorporated in the photographic elements. Those sulphonic acidderivatives of the aforesaid 2:4-diarylpyrroles and their salts whichare water-soluble are especially suitable for use in the developingsolution. Those color formers which are not sulphonic acid derivativesare frequently but sparingly soluble in water. Nevertheless, especiallywhen they contain other solubilising groups, for example phenol groups,they may frequently be incorporated in developing solutions by the useof suitable proportions of an organic solvent which is miscible purpose.Being also sparingly soluble in water they have little tendency todiffuse from the film into the processing solutions. The color formersof the invention may be incorporated in the photographic emulsions byany of the well known methods, for example by the processes described inBritish specifications Nos. 540,368 and 541,558.

The images obtained using the color formers of the invention are ofbright reddish blue to blue-green shades. These shades are of highintensity and, furthermore, they are of high intensity when, as isdesirably the case, photographic developing solutions are used whichcontain an alkali metal sulphite.

As is known, many of the blue-green images obtained from known colorformers, which should, ideally. transmit all light of 400-500 ma. wavelength do in fact absorb appreciably in this region. Thus for example inmaking copies from colored originals by methods in which no colorcorrection by masking is introduced, there is thereby introduced a shiftof hue whereby in effect there issuperimposed yellow over the blue areasof the copy. I have found that certain of the color formers of thisinvention, particularly those in which the aryl groups of the2:4-diaryipyrroles are substituted by chlorine atoms, give rise to dyeimages which show an improved transmission in the 400-500 ma, 1. e.,blue, region.

As illustrated in the examples which follow the photographic images areproduced in photograpic elements containing a reducible silver saltimage by development with an aromatic amino developing agent. But, asalready stated, alternative methods may be used. Thus an elementcontaining the color former may be treated with the oxidation product ofan aromatic amino developing agent. For example the color former may beincorporated in bichromate-sensitised colloid layers, for examplegelatin. gum arabic or albumen, the layers exposed, the unexposedcolloid removed, for example by treatment with hot water, and the colordeveloped in the exposed portions by treatment with ap-nitrosodialkylaniline or a derivative thereof.

Furthermore, photographic elements containing the color formers of theinvention may be treated with diazonium salts to form azo dyes. Thuswhen treatedwith benzene diazonium chloride the-color formers of thisinvention yield yellow or red dyes which may readily be differentiallybleached to form dye images, for example by the processes of Britishspecifications Nos. 133,034 and 496,558.

The invention is illustrated but not limited by the following examples:

Example 1 To 1000 cc. of a developer having the followthere is added 100ccs. of a solution of 1.0 gram of 2-phenyl-4-(m-hydroxylphenyl)pyrroleand 2.9 grams of sodium hydroxide in 100 cos. of a mixture of equalweights of water and ethanol.

When a photographic element containing reremoved from the element bysuccessive bathing in a 4% aqueous solution of potassium ferricyanideand in a 25% aqueous solution of sodium thiosulphate.

Example 2 1.0 gram of the sodium salt of 2-phenyl-4-(o-chlorophenyl)pyrrole monosulphonic acid is dissolved in 100 ccs. ofhot .water and the solution is added to 1000 cos. of the developingsolution vused in Example 1.

Whena photographic element containing reducible silver salts isdeveloped in,this solution a, clear greenish-blue dye image is producedtogether with metallic silver.

Example 3 1.0 gram of the ammonium salt of 2:4-diphenylpyrrolemonosulphonic acid is dissolved in a mixture of 50 ccs. of water and 50ccs. of acetone. A further 50 cos. of acetone are added to thesolutionand the resulting mixture is added to 1000 ccs. of a developerof the following composition:

Crystalline sodium sulphite grams 15.0 Asymmetric diethylp-phenyl-enediamine sulphate "grams" 3.0 Anhydrous sodium carbonate do40.0 Potassium bromide do 0.5 Water to ccs. 1,000

A photographic element containing a developable silver halidev imageistreated with the above solution and a bright blue dye image is obtainedtogether with the silver image.

Example 5 To 1000 ccs. of the developing solution used in Example 1thereis added 100 ccs. of acetone and the resulting mixture is employedas a developer for a photographic element containing a ducible silversalts is developed in this solution a bright greenish-blue dye image isproduced together with metallic silver. The silver may be reduciblesilver salt and also containing 2-phenyl- 4-(2-chlorophenyl) pyrrole inthe form of a fine uniform dispersion. A bright greenish-blue dye imageis obtained along with the silver image.

Photographic elements containing other color formers are developed inthe developing solution used in Example 5. The color of the dye imageobtained is shown in the table below:

Exall liple Color Former Color of image 6B-benzoylamino-zf-i-dipbenylpyrrole.... Blue. 7 2-phenyl-4(Pmethoxypheny )pyrrole Do. 8 2:4-dipheny pyrrole Do. 92-phenyl-4-(p-bromophenyl)pyrrole.. Do. 10 2-phenyl-4-(a-naphthyl)pyrrole Greenish-blue.

I claim: I,

1. A process for the production of a photographic dyestufi image whichcomprises developing a photographic element containing a reduciblesilver salt image with an aromatic primary amino color developing agentin the presence of a substituted 2 l-diarylpyrrole of the formula whereR and R stand for aryl radicals and R stands for a member of the groupconsisting of hydrogen, aryl, alkyl, alkylamino, benzylideneamino, andacylamino radicals.

2. A photographic element bearing an emulsion layer containing alight-sensitive material and a color former comprising a2:4-diarylpyrrole of the formula where R and R stand for aryl radicalsand R stands for a member of the group consisting of hydrogen, aryl,alkyl, alkylamnio, benzylideneamino, and acylamino radicals.

3. A photographic element bearinga light-senwhere R and R stand for arylradicals and R stands for a member of the group consisting of hydrogen,aryl, alkyl, alkylamino, benzylideneamino, and acylamino radicals. r

4'. A photographic developing solution containing an aromatic primaryamino color developing agent and a color former comprising a substituted2:4-diarylpyrrole of the formula Ru C Rm where R and R stand for ar ylradicals and R stands for a member of the group consisting of hydrogen,aryl, alkyl, alkylamino, benzylideneamino, and acylamino radicals.

DOUGLAS WILLIAM STAMNEERS.

